In recent years, for an ultrasound transducer (also called ultrasound probe or ultrasound probe) of an ultrasound diagnostic apparatus, piezoelectric micromachined ultrasound transducers (pMUTs) utilizing a micro electro mechanical system (MEMS) have been increasingly developed (see, for example, non PTL 1).
A piezoelectric cell (transducer, which is sometimes referred to also as pMUT cell below) used in a pMUT advantageously has high-frequency suitability and high sensitivity, but has a problem of its narrowband characteristics. In contrast, for example, the ultrasound transducer disclosed in PTL 1 achieves broadband in its entirety by arranging and simultaneously driving piezoelectric cells having resonance frequencies different from one another and each having narrowband characteristics. For example, in PTL 1, the spring constants (e.g., the area, thickness, material of the oscillation film and the like) of oscillation films of piezoelectric cells are set to values different from one another to acquire different resonance frequencies.